The care and treatment of severely premature babies has achieved a high degree of effectiveness, and further advances are to be expected. One important aspect of this care and treatment is in the control of the oxygen level of the air supplied to such babies at an elevated level. It has, however, been found that a high level of oxygen can lead to ROP. Careful control of the oxygen level is therefore required, but although this reduces the incidence of ROP, the need for a high oxygen level to maintain the general health of the baby means that there Is still an appreciable risk of ROP, a risk which rises to a high level for severe prematurity. Although there is substantially complete recovery of sight from ROP in most cases, it leads to complete blindness in a small but significant number of cases.
Premature babies may be exposed to high light levels, which may arise from a variety of causes such as sunlight, strong and continuous artificial ward light generally, and the use of phototherapy. There has been substantial speculation that the risk of ROP is increased by such exposure to high levels of light.
Phototherapy consists of exposing the baby to a high intensity white or short wavelength light for the treatment of neonatal jaundice (hyperbiliruminaemia). It is well known to "patch", i.e. blindfold, babies undergoing such treatment. The treatment lasts for periods in the region of 24 hours; patching may well reduce the chance of ROP developing, and is unlikely to have any harmful effects for that kind of length of time.
It has also been suggested that the general light intensity to which premature babies are subjected should be kept low, and an investigation has been carried out in which filters were placed over the incubators of certain premature babies, cutting the light intensity by about 50%. The results indicated that this reduced the incidence and severity of ROP. This investigation has, however, been criticized.
Studies have also been performed using animals, and some of the results of these also lend support to the view that high light levels damage the human eye. However, the precise relevance of these studies to ROP is unclear for a variety of reasons.
The general practice with premature babies is, therefore, to patch their eyes during phototherapy, but to take no further special measures to reduce the light levels to which they are exposed (though general awareness of the matter may result in a greater readiness to draw the curtains or blinds if there is strong sunshine into the ward, and caution when designing lighting systems for premature baby wards.
There have been no serious proposals to maintain premature babies in permanent darkness (either total body darkness or by patching). The major reasons for this are, probably, that total darkness makes it very difficult to monitor the baby; the effectiveness of permanent patching would be doubtful, as the blindfolds would be liable to become dislodged; parental dissatisfaction; and, of course, the well-known fact that, at least in certain animal species, exposure to light is essential for proper development of sight.